1. Field of the Invention
The present invention relates to a storage apparatus that provides a host apparatus with relevant controls for the host apparatus to store data in a storage unit. More specifically, the invention relates to a storage apparatus with a control function used when writing write data sent from a host apparatus to secondary volume(s).
2. Description of Related Art
A storage apparatus is an apparatus that is connected to host computer(s) and constitutes a storage control system, providing the host computer(s) with large-capacity storage areas. In that type of storage apparatus, a plurality of storage devices (e.g. hard disk drives) is installed in its case in arrays. The storage apparatus virtualizes its storage resources and provides them to the host computer(s). The host computer(s) recognize logical volumes, which are made by virtualizing physical storage areas, and write/read-access those logical volumes. In the above, the storage apparatus defines a RAID group composed of several storage devices to ensure data redundancy. The host computer(s) may directly be connected to the storage apparatus, or they may also be connected via a SAN or an IP communication network. Note that a storage apparatus like the above is also referred to as a storage subsystem or a storage controller.
An application program running on a host computer read/write-accesses volumes, and writes/reads the relevant data to/from a storage unit, which is a physical resource. A management apparatus attached to a storage apparatus is provided with a function for defining secondary volumes in the storage apparatus in association with primary volumes, which are write/read-accessed by the host computer(s).
A primary volume is an online volume that the host computer(s) can access online, while a secondary volume is the replica of a particular primary volume. A volume management program in a storage apparatus recognizes each secondary volume as a volume that is paired with a particular primary volume to mirror that primary volume, and a write/read management program in the storage apparatus writes the relevant write data for a write command sent from a host computer to both the primary and secondary volumes. As a result, data in a primary volume is made consistent with data in the corresponding secondary volume, and users of the storage apparatus can utilize the secondary volume as a backup volume. A secondary volume like the above is also referred to as a replicated volume or a mirror volume.
In storage apparatuses where secondary volumes can be set, a plurality of secondary volumes is required [for one primary volume] in some cases. For example, single or several users may need to use a plurality of secondary volumes—one for backup, one for testing, and one for batch processing, and so on. For example, JP 2006-031579 A discloses a storage apparatus that can generate a plurality of secondary volumes (N volumes) for one primary volume.